Electrical Test Device And Method

ABSTRACT

An electrical test device may include a power supply, a conductive probe element, and a spectral analysis block. The power supply may be connected to an external power source. The conductive probe element may be connected to the power supply and may be configured to be energized by the power supply. The probe element may be configured to be placed in contact with an electrical system under test and apply an input signal containing current for measuring at least one parameter of the electrical system. The spectral analysis block may be connected to the probe element and may be configured to receive an output signal from the electrical system in response to the application of the current to the electrical system. The spectral analysis block may be configured to analyze frequency spectra of the output signal and detect a broadband increase in energy of the frequency spectra above a predetermined energy threshold. The broadband increase in energy may be representative of the occurrence of arcing in the electrical system.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is related to U.S. Pat. No. 7,184,899, issued onFeb. 27, 2007 to Randy Cruz, and which is entitled ENERGIZABLEELECTRICAL TEST DEVICE FOR MEASURING CURRENT AND RESISTANCE OF ANELECTRICAL CIRCUIT, and to U.S. Pat. No. 5,367,250, issued on Nov. 22,1994 to Jeff Whisenand, and which is entitled ELECTRICAL TESTER WITHELECTRICAL ENERGIZABLE TEST PROBE, the entire contents of U.S. Pat. Nos.7,184,899 and 5,367,250 being expressly incorporated by referenceherein.

FIELD

The present disclosure relates generally to electrical test equipmentand, more particularly, to an electrical test device configured todiagnose one or more faults in an electrical system under test duringthe application of current to the electrical system.

BACKGROUND

Motor vehicles such as automobiles are increasingly dependant uponelectronic circuitry for operation and require increasing levels ofsophistication to efficiently diagnose and repair such motor vehicles. Awide variety of faults may occur in automotive electrical systemsincluding short circuits, open circuits, and failed components such asfailed connections, relays, switches, and computer modules. Another typeof fault that may occur in electrical systems is arcing. Arcing may bedefined as unwanted electric spark or arc jumping a gap between twoisolated nodes or conductors and may occur on an intermittent orimpulsive basis within an electrical system.

Arcing may be caused be the presence of solid or liquid contamination,by the presence of moisture in an electrical system, by carbon tracksfrom decaying plastics, and by other causes, all of which may lead to anincreased probability of an electric spark jumping a gap between twoisolated nodes. The occurrence of arcing may lead to improper operationand/or damage to the electrical system which may include pitting in arelay, surface damage to a conductor, premature electrical failure, orfire.

Known conventional multi-meters lack the capability to detect theoccurrence of arcing. Because arcing can be the cause of an existingfailure in an electrical system or a potential failure in an electricalsystem, the ability to identify and detect the occurrence of arcing ishighly beneficial. For example, the ability to identify and detect theoccurrence of arcing may allow a technician to diagnose and repair amalfunction in an electrical system before permanent damage occurs. Inaddition, the identification of arcing can itself be an indicator thatpermanent failure has occurred in an electrical system such that thetechnician may then repair or replace a damaged component or module.

Another type of fault that may be difficult to detect in an electricalsystem is a loss of integrity in low-resistance or low-impedanceelectrical paths that carry relatively high-amperage current to variouslocations within the electrical system. For example, such electricalpaths may include a battery cable of a motor vehicle carrying currentfrom the battery to the starter. The electrical resistance of suchcables is relatively low due to the large diameter of such cables makingmeasurement of the resistance difficult using conventional multi-meters.Specialized micro-ohm meters may be used to measure the resistance insuch cables. Unfortunately, the testing of a low-resistance cable usinga micro-ohm meter typically requires the disconnection or removal of thecable from the electrical system. Furthermore, such micro-ohm meters mayapply a relatively high-amperage test current to the cable which coulddamage sensitive electrical components if the high-amperage test currentwere inadvertently applied for an extended period of time.

As can be seen, there exists a need in the art for a system and methodfor detecting the presence of arcing in an electrical system. Inaddition, there exists a need in the art for evaluating the integrity ofrelatively low-resistance electrical paths or cables of an electricalsystem. Furthermore, there exists a need in the art for evaluating theintegrity of relatively low-resistance electrical paths or cableswithout requiring the disconnection or removal of such electrical pathsor cables from the electrical system.

BRIEF SUMMARY

The above-noted needs associated with electrical test devices arespecifically addressed and alleviated by the present disclosure which,in an embodiment, provides a test device comprising a power supply, aconductive probe element, and a spectral analyzer. The power supply maybe connected to an external power source. The conductive probe elementmay be configured to be energized by the power supply and may be placedin contact with an electrical system for application of an input signalcontaining current for measuring at least one parameter of theelectrical system. The spectral analyzer may be connected to the probeelement and may be configured to receive an output signal from theelectrical system in response to the application of the input signal.The spectral analyzer may analyze the frequency spectra of the outputsignal. The frequency spectra may have a low-frequency portion and ahigh-frequency portion and may contain energy contributed by periodicsignals and non-periodic signals. The spectral analyzer may analyze thelow-frequency portion and detect the potential occurrence of arcing whenthe energy contributed by the non-periodic signals exceeds apredetermined energy threshold in the low-frequency portion. Thespectral analyzer may then analyze the high-frequency portion when theenergy in the low-frequency portion exceeds the energy threshold. Thespectral analyzer may detect the occurrence of arcing in the electricalsystem when the energy in the high-frequency portion exceeds the energythreshold.

Also disclosed is a method of detecting arcing in an electrical system.The method may comprise the step of placing a probe element in contactwith an electrical system. The method may further include the step ofproviding power to the probe element from an external power source. Aninput signal containing current may be applied to the electrical systemsuch as by using a probe element. The method may include the step ofreceiving an output signal from the electrical system in response to theapplication of the input signal. The method may further includeanalyzing the frequency spectra of the output signal wherein thefrequency spectra has a low-frequency portion and a high-frequencyportion and contains energy contributed by the periodic and non-periodicsignals. The method may include analyzing the low-frequency portion anddetecting the potential occurrence of arcing in the electrical systemwhen the energy contributed by the non-periodic signals in thelow-frequency portion exceeds a predetermined energy threshold. Inaddition, the method may include analyzing the high-frequency portionwhen the energy in the low-frequency portion exceeds the energythreshold. The occurrence of arcing in the electrical system may bedetermined when the energy in the high-frequency portion exceeds theenergy threshold.

Also disclosed is a test device for assessing or testing the integrityof a relatively low-impedance electrical path such as a cable. The testdevice may include a power supply, a probe element, and a processor. Thepower supply may be connected to an external power source. The probeelement may be placed in contact with the electrical path and may beenergized by the power supply for applying an input signal of relativelylow amperage to the electrical path. The processor may receive an outputsignal from the electrical path and determine a first voltage across theelectrical path in response to application of the low-amperage inputsignal. The processor may further be configured to apply a relativelyhigh-amperage current pulse to the electrical path and determine asecond voltage across the electrical path in response to application ofthe high-amperage current pulse. In addition, the processor maydetermine a volt drop across the electrical path based upon thedifference between the first voltage and the second voltage. Theprocessor may calculate an electrical resistance of the electrical pathbased upon the voltage drop.

Also disclosed is a method of measuring a voltage drop in a relativelylow-impedance electrical path. The method may comprise the steps ofplacing a probe element in contact with the electrical path. The probeelement may be energized from a power supply. A relatively low-amperageinput signal may be applied to the electrical path using the probeelement. The method may include determining a first voltage across anelectrical path in response to application of the low-amperage inputsignal. The method may further include applying a relativelyhigh-amperage current pulse to the electrical path and determining asecond voltage across the electrical path in response to the applicationof the high-amperage current pulse. The method may additionally includedetermining a voltage drop across the electrical path based upon thedifference between the first voltage and the second voltage. The methodmay further include providing a pass/fail notification regarding whetherthe measured voltage drop exceeds a maximum specified voltage drop forthe electrical path. Alternatively, the method may include providing apass/fail indication of whether the calculated electrical resistance ofthe electrical path falls within a specified operating range.

The features, functions and advantages that have been discussed can beachieved independently in various embodiments of the present disclosureor may be combined in yet other embodiments, further details of whichcan be seen with reference to the following description and drawingsbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the present disclosure will become moreapparent upon reference to the drawings wherein like numerals refer tolike parts throughout and wherein:

FIG. 1 is a block diagram of an embodiment of an electrical test deviceand which may include a power supply, a processor, a display device, akeypad, and an energizable probe element;

FIG. 2 is a perspective illustration of an embodiment of the electricaltest device illustrating a pair of power leads and a ground lead thatmay be included with the electrical test device;

FIG. 3 is a partially exploded perspective illustration of the testdevice showing a circuit board assembly and having the power cable andthe probe element extending out of the housing;

FIG. 4 is a top view illustration of the electrical test device showingan auxiliary cable that may be connectable to the electrical testdevice;

FIG. 5 is an end view of the electrical test device showing illuminatinglamps and an auxiliary jack formed within the housing for receiving theauxiliary cable;

FIG. 6 is a flow diagram including one or more operations that may beincluded in a method for detecting the presence of arcing in anelectrical system; and

FIG. 7 is a of plot of the frequency spectra of an output signal inresponse to the application of current to an electrical system undertest and illustrating a low-frequency portion and a high-frequencyportion of the frequency spectra;

FIG. 8 is a flow diagram having one or more operations that may beincluded in a method of detecting a voltage drop in an electrical pathof an electrical system;

FIG. 9A is an illustration of an electrical path configured as a powerground having a high-voltage side and a low-voltage side andillustrating the probe element placed in contact with the high-voltageside for testing of the voltage drop;

FIG. 9B is an illustration of an electrical path configured as a powerfeed and illustrating the probe element placed in contact with thelow-voltage side for testing of the voltage drop; and

FIG. 10 is a flow chart illustrating one or more operations that may beautomatically performed during measurement one or more parameters of anelectrical system under test.

DETAILED DESCRIPTION

Referring now to the drawings wherein the showings are for purposes ofillustrating various aspects of the present disclosure, shown in FIG. 1is an electrical test device 10 that is configured for providing currentsourcing or power to an electrical system 150 under test whilesimultaneously providing multi-meter functionality for measurement ofone or more parameters of the electrical system 150. In addition, theelectrical test device 10 disclosed herein is configured to monitor theelectrical system 150 under test for arcing behavior in the presence ofnon-arcing signals while simultaneously measuring one or more parametersof the electrical system 150.

The electrical test device 10 disclosed herein is also configured tomeasure the integrity of low-impedance or low-resistance electricalpaths 156 (FIGS. 9A-9B) such as a battery cable (not shown) extendingbetween a battery (not shown) and a starter (not shown) of a motorvehicle (not shown). Advantageously, the test device 10 provides a meansfor measuring electrical resistance in low-impedance electrical paths156 by providing a relatively high-amperage current pulse to generate avoltage drop that can be accurately measured. Once the voltage drop hasbeen acquired, the test device 10 may calculate the electricalresistance and determine whether an electrical path 156 or cable isfunctioning properly. Advantageously, the determination of theelectrical resistance of such electrical path 156 using the test device10 disclosed herein may be performed without disconnecting or removingthe suspect electrical path 156 or cable.

The test device 10, advantageously, may also allow for automaticallydetecting and/or sequentially measuring several parameters of anelectrical system 150 without user intervention. More particularly, thetest device 10 is configured to allow for sequentially moving throughthe measurement of one or more parameters including, but not limited to,voltage, resistance, frequency, and other parameters. The test device 10may measure and display one or more parameters for which a signal isavailable or for which testing conditions facilitate the measurement ofsuch parameters. In this regard, the test device 10 is configured toallow the sequential measurement of several parameters without requiringmanual manipulation or selection of the parameter to be measured.

In any one of the embodiments disclosed herein, the test device 10 maybe configured to provide current flow through an electrical system 150and may characterize or measure one or more parameters of the electricalsystem 150 including, but not limited to, impedance, wave form (e.g.,fluctuation, frequency/speed), and current drain in addition tomeasurements performed by conventional multi-meters such as voltage,current, and electrical resistance. Advantageously, the uniqueconfiguration of the test device 10 disclosed herein eliminates the needfor clip-on current sensors as may be required in conventionalelectrical test devices 10. In addition, the unique configuration of theelectrical test device 10 as disclosed herein may eliminate the need fora separate power cable and probe element 50 connection.

Referring to FIG. 1, shown is a block diagram of the electrical testdevice 10 which may comprise a conducive probe element 50, a powersupply 88, a processor 92, and a display device 54. Importantly, thetest device 10 may be configured to allow for selective powering of theelectrical system 150 under test upon energization of the probe element50 while parameters of the electrical system 150 are being measured. Inthe block diagram, shown are several functional blocks corresponding tothe various measurement capabilities of the test device 10. Each one ofthe functional blocks may be integrated with the processor 92 or may beunder the control of the processor 92 which, as is shown in FIG. 1, maybe configured as a microprocessor. The conductive probe element 50 maybe coupled to the processor 92 and/or one or more of the functionalblocks. The probe element 50 may be configured to be placed in contactwith the electrical system 150 under test and provide an input signal tothe electrical system 150. The probe element 50 may be connected to apower supply 88 which may receive power from external power source 90.The power source may be a battery such as a battery of a motor vehiclecontaining the electrical system 150 under test. However, the externalpower source 90 is not limited to a battery of a motor vehicle and maybe provided in alternative configurations.

Referring still to FIG. 1, the power supply 88 may be connected to areset control such as a microprocessor reset control 94. Themicroprocessor reset control 94 may be comprised of circuitry that mayprovide a reset signal to the processor 92 or microprocessor undercertain conditions such as when the operating voltage is out oftolerance. The power supply 88 is preferably configured to provide avoltage-regulated output for all circuitry contained within theelectrical test device 10. Preferably, the voltage-regulated output maybe provided independent of any input signal to the electrical system150.

The microprocessor reset control 94 may be electrically connected to theprocessor 92 or microprocessor. The processor 92 or microprocessor maybe electrically connected to the probe element 50 and may be configuredto manipulate the input signal that is provided to the electrical system150 and to receive the output signal in response to application of theinput signal. The output signal may be representative of the measurementof at least one or more of the parameters of the electrical system 150under test as indicated above. In manipulating and controlling theelectrical test device 10 measurement functions, the processor 92 ormicroprocessor may be provided with an executable software programconfigured to provide control of the various measurement processes ofthe electrical test device 10. In this manner, the processor 92 ormicroprocessor may regulate or control substantially all of thefunctions of the electrical test device 10.

In FIG. 1, the electrical test device 10 may include a display device 54which may be electrically connected to the processor 92 ormicroprocessor. The display device 54 may be configured to display areading or indication of the output signal that may be extracted fromthe electrical system 150 during testing. The reading on the displaydevice 54 may be representative of the parameter being measured.However, the test device 10 may also include an audible device forproviding an audible indication of operating parameters being measuredin the electrical system 150. For example, the audible device maycomprise a piezo element such as a piezo disk. The piezo disk may act asa speaker 66 for providing an indication regarding continuitymeasurements and/or voltage polarity of the electrical system 150 undertest.

As was earlier indicated, the electrical test device 10 may beconfigured to allow for selective powering or current sourcing to theelectrical system 150 upon energization of the probe element 50 duringmeasurement of the parameters of the electrical system 150. In thisregard, the electrical test device 10 may be configured to automaticallyswitch between an active mode and a passive mode. The active mode may bedefined by measurement of one or more parameters of the electricalsystem 150 during the application of current or power to the electricalsystem 150. As was previously indicated, such current or power mayultimately be supplied by an external power source 90 and which may bepassed through the power supply 88 and into the probe element 50. Inthis manner, the probe element 50 may apply current to the electricalsystem 150 under test. The passive mode of the electrical test device 10may be defined by measurement of one or more parameters of theelectrical system 150 without the application of power or current to theelectrical system 150. The application of power or current to theelectrical system 150 may be controlled by a button or switch on thekeypad or on the display device 54 and which may be connected to theprocessor 92 or microprocessor as illustrated in FIG. 1. The displaydevice 54 may operative to indicate whether the test device 10 is in thepassive mode or in the active mode.

In an embodiment, the display device 54 may be configured as a liquidcrystal display or any other suitable configuration of the displaydevice 54. The test device 10 may also include a speaker driver that maybe connected to the speaker 66 (e.g., the piezo element) and which mayformat and convert signals received from the processor 92 ormicroprocessor such that the speaker 66 may provide audible indications.In this same regard, the display driver illustrated in FIG. 1 may beconnected between the processor 92 or microprocessor and/or the displaydevice 54 and may also format and convert signals from the processor 92or microprocessor into a format required for display by the displaydevice 54.

Referring still to FIG. 1, shown are the functional blocks that may berepresentative of the measurement capabilities and features of the testdevice 10. Included with the functional blocks are a dual continuitytester 118, load impedance detector 120, logic probe detector andgenerator 122, frequency and totalizer measurement 124, voltagemeasurement 126, resistance measurement 132, programmable referencevoltage 133, power output driver with over current protection 128,current measurement with analog/digital (A/D) conversion 130, andspectral analyzer 134. Advantageously, due to the unique configurationof the test device 10 illustrated in the block diagram in the FIG. 1,the test device 10 may simultaneously measure current, voltage, andother parameters of the electrical system 150 during the application ofcurrent sourcing into the electrical system 150 under test.

Although each one of the functional blocks is indicated as a separateblock, componentry may be shared between the functional blocks tofacilitate one or more measurements of the electrical system 150.Furthermore, as shown in FIG. 1, each one of the functional blocks maybe connected to or integrated with the processor 92 or microprocessorwhich may control the overall operation of the electrical test device10. The dual continuity tester 118 functionality block shown in FIG. 1may be used in conjunction with the current source provided by the probeelement 50 when energized by the power supply 88. The electrical testdevice 10 disclosed herein is related to U.S. Pat. No. 5,367,250, issuedto Jeff Whisenand on Nov. 22, 1994 and which is entitled “ElectricalTester with Electrical Energizable Test Probe”, herein incorporated byreference in its entirety. The test device 10 disclosed herein is alsorelated to U.S. Pat. No. 7,184,899, issued on Feb. 27, 2007 to RandyCruz, and which is entitled “Energizable Electrical Test device 10 forMeasuring Current and Resistance of an Electrical Circuit”, hereinincorporated by reference in its entirety.

Referring to FIG. 1, the test device 10 disclosed may include the dualcontinuity tester 118 which may operate in conjunction with one or moresignal lamps 58 to provide a convenient means for testing thefunctionality of multi-pole relays (not shown). More specifically, thedual continuity tester 118 as incorporated into the test device 10 shownin FIG. 1 may be configured to allow for testing of multiple contacts(not shown) with the pressing of a single button on the keyboard whereinthe coil resistance of a relay may be easily measured. In addition,other test parameters may be obtained. The dual continuity tester 118,when coupled with the measurement functionality of the test device 10,enables the testing of contact switches (not shown) and relay devices.For example, in an electrical system 150 having two relays, the dualcontinuity tester 118 may provide for the capability of determiningwhich one of two relays is activated and/or which one of the relays isdeactivated. In this manner, the dual continuity tester 118 allows forchecking of relays using a pair of signal lamps 58 or using otherindicating means. When testing relays or switches, the speaker 66 maypreferably be inoperative in order to avoid producing audible signalsthat may otherwise interfere with detection of noises in the relayswitches and which may be indicative of a properly-functioning switch.However, the signal lamps 58 and/or the audible device may be used toprovide an indication as to the activated or deactivated state of therelays. Furthermore, the dual continuity tester 118 may facilitate thechecking of the status and operability of multiple contacts such as in amulti-pole/multi-contact relay or switch.

Referring still to FIG. 1, the load impedance detector 120 functionalblock allows for measurement of the magnitude of a voltage drop in anelectrical system 150 such as when testing electrical junctions in anelectrical circuit. The load impedance detector 120 functional block mayfacilitate testing a power feed 164 that may have loose or corrodedconnections. As will be described in greater detail below, when theprobe element 50 is connected to the electrical system 150 under test,the impedance of the electrical system 150 may be tested and theelectrical test device 10 may provide an indication, either audibly viathe speaker 66 and/or visually via the display device 54 (i.e., the LCD56), when a set point (i.e., a predetermined voltage level) is above amaximum specified voltage limit. The predetermined voltage level may beadjusted using the programmable reference voltage 133 block shown inFIG. 1.

The logic probe generator and detector 122 functional block may comprisea circuit that creates a sequence for outputting a signal into a device(not shown) of the electrical system 150 through the probe element 50.For example, a digital pulse train may be inputted into a device of theelectrical system 150 with the digital pulse train inserted into aterminal of a device under test in order to assess communication betweencomponents of the electrical system 150 (e.g., between an odometer of amotor vehicle in communication with a control unit of the motorvehicle). The logic probe generator and detector 122 functionality mayalso provide the electrical test device 10 with the capability tomeasure signal levels as well as frequency. High and low logic levelsmay be generated as well as pulse trains at various frequencies.

The frequency and totalizer measurement 124 functional block may allowthe electrical test device 10 to assess the rate of voltage or currentfluctuation in the electrical system 150 under test, and to accumulateoccurrences of a particular state over time. Circuitry of the frequencyand totalizer measurement 124 block may allow for processing of signaltransition of a waveform in order to extract the frequency, revolutionsper minute (RPM), duty cycle and number of pulses from a signal. Thefrequency aspect of the frequency and totalizer measurement 124functional block may allow for determining the frequency or RPM or dutycycle component of the electrical system 150. The totalizer aspect ofthe frequency and totalizer measurement 124 functional block mayaccumulate pulses or cycles and allows the electrical test device 10 tomeasure and check for intermittent output signals from the electricalsystem 150 under test. The frequency and totalizer measurement 124functional block may also provide a means for checking switches in anelectrical system 150 by providing a means for measuring the number oftimes that a contact within a switch bounces, for example, such as mayoccur in a relay switch.

The voltage measurement 126 block may allow for high speed voltagemeasurement 126 in the electrical system 150. The voltage measurement126 block may represent the ability of the electrical test device 10 tosample and detect positive and negative peaks of a signal as well asdetecting and measuring an average of the signals and displaying resultsof the signal readout on the display device 54. The voltage measurement126 block may simplify voltage drop tests, voltage transient tests, andvoltage fluctuation or ripple tests. The power output driver with overcurrent protection 128 functional block may provide a buffer stage or atransistor for the electrical test device 10 such that the power outputdriver with over current protection 128 may regulate the amount ofcurrent that may be passed from the power supply 88 to the probe element50 and ultimately into the electrical system 150 under test. Inaddition, the power output driver 128 may establish an appropriate driveimpedance and protect the electrical test device 10 from damage due toautomotive transients. The current measurement 130 functional block mayallow for high speed current measurement 130 by the electrical testdevice 10 such as sampling and detection of current consumed in a loadprovided in the input signal which is inserted into the electricalsystem 150. Such consumed current may be displayed on the display device54.

Referring now to FIGS. 2-5, shown is an embodiment of the electricaltest device 10 schematically illustrated in FIG. 1. As best shown inFIGS. 2-3, the electrical test device 10 may include a housing 14configured as a generally elongated, hollow, rectangular cross-sectionalbox. The housing 14 may have a top end 20 and a bottom end 22. The topend 20 may be generally wider than a remaining portion of the housing 14so that a display assembly 52 containing the display device 54 may beincorporated into the housing 14. The display device 54 may be supportedwith display supports 44 which may orient the display device 54 at aconvenient angle for observation by an operator of the test device 10.The remaining portion of the housing 14 may have a narrower width toallow for single-hand operation of the test device 10.

Contained within the housing 14 may be a circuit board assembly 36comprising a circuit board 38 whereon the microprocessor 40 and thedisplay device 54 along with the power supply 88, the microprocessor 40reset control 94, the speaker driver 68, and the display driver 96 maybe enclosed and interconnected. The housing 14 may include an uppershell 18 and a lower shell 16 which may be fastened to one another suchas by mechanical fasteners. As can be seen in FIGS. 2 and 3, the housing14 may include an upper wall 24 disposed with the upper shell 18 and alower wall 26 disposed with the lower shell 16. In its assembled state,the housing 14 may include opposing side walls 28 and opposing end walls30. At the top end 20 of the housing 14 may be an aperture formedtherein and into which a probe jack 98 may be fitted. The probe element50 may be configured to be removably inserted into the probe jack 98. Aprobe overmold 46 may be provided to encase a major portion of the probeelement 50.

At the bottom end 22 of the housing 14 may be another aperture formedtherein and through which a power cable 78 may protrude. The power cable78 may be configured with a pair of power leads 80, preferably onepositive lead and one negative lead. In addition, a ground lead 82 maybe also included in the power cable 78 extending out of the bottom end22 of the housing 14. Both power leads 80 may be configured as insulatedconductors as may be the ground lead. The cable 50 may be encased in acable sheathing 86 which passes through an annular shaped bushing 72coaxially fitted within the aperture formed in the end wall 30 and whichmay prevent undue strain on the cable 50. The cable 50 may include aproximal end 104 which may be disposed adjacent the housing 14 apertureand the strain relief bushing 72. The cable 50 may also include a distalend 106 having a pair of high power alligator clips 76 disposed onextreme ends of each one of the power leads 80.

As was earlier mentioned, the external power source 90 may be configuredas a motor vehicle battery (not shown) with the alligator clips 76 beingconfigured to facilitate connection thereto. The alligator clips 76 maybe color-coded wherein a negative one of the power leads 80 may beprovided in a black-colored alligator clip 76 and the positive one ofthe power leads 80 may be provided with a red-colored alligator clip 76.Disposed at an end of the ground lead 82 may also be an alligator clip76 to facilitate connection to a ground source. As can be seen in FIG.2, the upper and lower shells 16, 18 of the housing 14 are configured toprovide a hang loop 34 extending out of one of the side wall 28. Thehang loop 34 may provide a mechanism by which the electrical test device10 may be attached to or hung from fixed objects such as a cable or ahook.

As shown in FIG. 3, the power cable 78 may be electrically connected tothe circuit board assembly 36. As was previously mentioned in thedescription of FIG. 1, the external power source 90 may be connected viathe power cable 78 to a power supply 88 which may be integrated with thecircuit board assembly 36 and which is ultimately connected to the probeelement 50 extending out of the top end 20 of the housing 14. Includedwith the probe element 50 may be a probe tip 48 on an extreme endthereof. Advantageously, the probe element 50 may be configured to beremovable from the electrical test device 10 via a probe jack 98 suchthat various electrical testing accessories may be plugged into theprobe jack 98 for checking the electrical system 150 under test.

Referring now to FIG. 5, shown is a front view of the electrical testdevice 10 and illustrating openings or apertures formed within thehousing 14 through which illumination lamps 60 may at least partiallyextend. The illumination lamps 60 may optionally be provided forilluminating an area adjacent to the test device 10. Although fourapertures and illumination lamps 60 are shown, any number may beprovided. It is contemplated that the illumination lamp 60 or lamps maybe configured as light emitting diodes 64 (LEDs). Activation anddeactivation of the illumination lamps 60 may be provided by means ofthe keypad 84 which may be electrically connected to the processor 92 ormicroprocessor 40 located on the circuit board 38 and which may bedisposed at a location adjacent to the display device 54.

Also shown in FIGS. 4-5 is an auxiliary jack 100 into which an auxiliarycable 102 may be inserted for facilitating continuity measurements aswas described above with regard to the dual continuity tester 118functionality block. The auxiliary cable 102 has a proximal end 104 anda distal end 106 and may comprise a pair of auxiliary test leads 108 andthe auxiliary ground lead 110. The auxiliary test leads 108 may comprisea first continuity test lead 112 and a second continuity test lead 114.In addition, the auxiliary cable 102 may include an auxiliary groundlead 110 for use as a continuity test common ground 116. The auxiliaryjack 100 formed within the housing 14 may be electrically connected tothe processor 92 or microprocessor 40. As was previously mentioned, theauxiliary ground and test leads 110, 108 may be adapted to beselectively insertable into the auxiliary jack 100 at the proximal end104.

Referring to FIG. 3, mounted with the housing 14 may be the displaydevice 54 which may be configured as a liquid crystal display 56 (LCD).In order to protect the display device 54 as well as the interior of thehousing 14, a display overlay 12 may be included and is preferablydisposed generally flush or level with an upper wall 24 of the housing14. In addition, the display overlay 12 may extend along the upper shell18 to form a protective barrier for the keypad 84 integrated into theelectrical test device 10. As was earlier mentioned, the keypad 84 mayallow for manipulation of the processor 92 or microprocessor 40 forcontrolling the functionality of the electrical test device 10. Thekeypad 84 may be comprised of any number of keys or buttons butpreferably may include three (3) buttons for operation of the electricaltest device 10. The three (3) buttons of the keypad 84 may be preferablyconfigured to allow for selective switching between differentmeasurement modes of the electrical test device 10.

In addition, the keypad 84 may allow for the measuring and displayingvarious parameters such as AC voltage and DC voltage measurements,resistance of an electrical circuit, current flowing within anelectrical circuit, the frequency of signals, and any other parametermeasured by any one of the test device 10 embodiments disclosed herein.In an embodiment, the electrical test device 10 may be manipulated suchthat parameters measurable by the electrical test device 10 include atleast one of the following: circuit continuity, resistance, voltage,current, load impedance, and frequency, RPM, and pulse counting. Inaddition, further measurement modes may be facilitated throughmanipulation of the keypad 84. For example, frequency, RPM, duty cycle,and totalizer measurements may be extracted from an electrical system150 under test. In addition, signal level and frequency may be measuredas well as testing of impedance.

Referring still to FIG. 3, shown included with the circuit boardassembly 36 may be at least one fuse 42 and preferably a pair of fuses42 which partially protrude through apertures formed in the housing 14at the upper shell 18. The fuses 42 may be incorporated into theelectrical test device 10 as a safety precaution to prevent damage tothe circuitry of the test device 10. Also included with the electricaltest device 10 may be a circuit breaker 62 such as an electronic circuitbreaker 62 which may also have configurable trip levels and a manualcircuit breaker reset. Also shown incorporated into the circuit boardassembly 36 of the electrical test device 10 is a piezo element 70 whichis shown configured as a piezo disk 74 and which is disposed adjacentthe bottom end 22 of the housing 14.

Speaker 66 holes 32 may be formed in the upper shell 18 of the housing14 to allow for transmission of audible tones generated by the piezodisk 74 during operation of the electrical test device 10. Also includedwith the circuit board assembly 36 may be an additional lamp configuredas an LED 64 and which may protrude through an aperture formed in theupper shell 18 of the housing 14 as shown in FIGS. 2 and 3. Such LED 64may be connected to the processor 92 or microprocessor 40 and mayprovide a means to indicate whether power is being applied to theelectrical test device 10. Alternatively, or in addition to, the LED 64protruding through the upper shell 18 of the housing 14 may also beconfigured as a power-good indicator and may be de-activated to alertthe user of a blown fuse 42.

Regarding the operation of the electrical test device 10, as was earlierdiscussed, the electrical test device 10 is operative in either one of apassive mode or an active mode. The passive mode is defined bymeasurements of parameters of an electrical system 150 with no powerbeing supplied thereto by the probe element 50. The active mode isdefined by measurement of parameters of the electrical system 150 duringapplication of power such as from an external power source 90 throughthe probe element 50 and into the electrical system 150.

As was earlier discussed, the electrical test device 10 may be operatedas a dual continuity tester 118 wherein the auxiliary cable 102 may beinserted into the auxiliary jack 100 at the top end 20 of the housing 14as shown in FIG. 4. After insertion, the first continuity test lead 112and second continuity test lead 114 as well as continuity test commonground 116 may be connected to the electrical system 150 under test. Inthe active mode, wherein power is supplied to the electrical system 150under test, the continuity of a particular portion of the electricalsystem 150 may be verified by using the auxiliary cable 102 comprisingthe first continuity test lead 112 and/or the second continuity testlead 114 in combination with the continuity test common ground 116.

As shown in FIG. 3, a pair of signal lamps 58 may be included with thetest device 10 and may be positioned at the top end 20 of the housing 14so as to protrude through apertures formed in the upper shell 18. Thesignal lamps 58 may be configured as LEDs 64 and, more specifically, maybe configured as a green LED and a red LED. In addition, as waspreviously mentioned, the piezo element 70 may be used in combinationwith or may be exclusively during continuity testing. Importantly, thedual continuity tester 118 may use the current source provided by theexternal power source 90 for inputting current into the electricalsystem 150 during continuity testing.

Load impedance detection 120 (FIG. 1) functionality may be facilitatedsuch that the magnitude of a voltage drop within an electrical system150 (FIG. 1) may be determined such as when testing electrical junctionsin power feed circuits that may have loose or corroded connections. Theelectrical system 150 under test may be measured with differencestherebetween being assessed and displayed on the display device 54 (FIG.1). The logic probe generator and detector 122 functional block, as waspreviously discussed, allows for testing of high logic, low logic, andpulsing logic signals. The electrical test device 10 is configured toallow forcing of the input signal into the electrical system 150 undertest with manipulation of multiple functions of the logic detectionfunctionality such that an appropriate input signal may be injected intothe electrical system 150 under test.

The frequency and totalizer measurement 124 (FIG. 1) functionality mayallow for measuring signals from the electrical system 150 as well asproviding the capability for entering a “divide ratio”, which may beequivalent to the number of cylinders of an engine of the motor vehiclebeing tested. In this manner, the electrical test device 10 may measurethe revolutionary speed at which a motor vehicle engine is operating. Inaddition, as was previously discussed, rates of voltage or currentfluctuation may be measured and signal transition components of a waveform may be analyzed to extract frequency, duty cycle, and number ofpulses. Regarding the voltage measurement 126 functionality, theelectrical test device 10 may measure and display average voltage aswell as measure and display positive peak voltage and negative peakvoltage. Importantly, the measurement of negative peak voltage enhancesthe ability to analyze and measure voltage of an alternator having afaulty diode.

The electrical test device 10 may be operated as a digital volt meterfor performing a voltage drop test and battery load test as well astransient voltage testing. In addition, the combination of the poweroutput driver 128 with current measurement 130 (FIG. 1) capability mayallow the electrical test device 10 to measure current and voltagesimultaneously. The electrical test device 10 may be placed in theactive mode wherein a button of the keypad 84 may be placed in a“latched” mode or permanent operation mode wherein a constant supply ofpower is provided into the electrical system 150 under test through theprobe element 50. However, the electrical test device 10 can be placedin a “momentary” power mode wherein power may be supplied on anas-requested basis by to manual manipulation of one of the buttons ofthe keypad 84.

The processor 92 or microprocessor 40 may be configured to causeperiodic energization of the probe element 50 for powering theelectrical system 150 under test at predetermined intervals for testingan electro-mechanical device that is part of an electrical system 150under test. Examples of electro-mechanical devices that may be tested inthis manner include, but are not limited to, relay switches, solenoids,motors, and various other devices. Power may be provided to theelectrical system 150 under test on an automatic intermittent basis atpredetermined intervals such as, for example, at one-second intervals orat other intervals. Advantageously, the ability to provide power in suchvarying modes allows for testing the proper operation ofelectro-mechanical devices such as relay switches as well as tracing thelocations of such electro-mechanical devices. By connecting theelectrical test device 10 to the external power source 90 andintermittently providing current into the electrical system 150 throughthe probe element 50, a user may track the location of a faulty relayswitch by listening for a clicking sound as power or current isintermittently applied to the electrical system 150 under test. Suchmethod for checking for faulty relay switches may be especially valuablein detecting a relay switches that may be hidden underneath carpeting,seating, and/or plastic or metal molding commonly found in automotiveinteriors.

Referring still to FIG. 1, the electrical test device 10 disclosedherein is configured to monitor an electrical system 150 for arcingwhile simultaneously measuring one or more parameters of the electricalsystem 150 such as during the application of current to the electricalsystem 150. FIG. 1 graphically illustrates an arc 154 occurring betweenthe electrical system 150 under test and a component 152 that isassociated with the electrical system 150. In the test device 10, thespectral analyzer 134 block may cooperate with the power output driverwith over current protection 128 block and the frequency and totalizermeasurement 124 block to detect arcing in the electrical system 150.Furthermore, the above-noted functional blocks may be operative to haltthe application of current or power to the electrical system 150 in theevent that arcing is detected. The above-noted functional blocks maycooperate to measure the time-varying nature (i.e., time domain) and thefrequency spectrum (i.e., frequency domain) of the parameters beingmeasured. In this regard, the test device 10 may analyze the frequencyspectrum of an output signal to determine whether arcing is occurring bydistinguishing non-periodic signals 144 (i.e., arcing signals) fromperiodic signals 142 such as AC voltage, DC voltage, logic/datawaveforms, and other signals which may have spectral energy that may bemore contained in a low-frequency portion of the frequency spectrum ofan output signal.

As indicated earlier, an arc 154 (FIG. 1) may be defined as an impulseof relatively short duration in the time domain and which may occur oneor more times during the operation of an electrical system 150 dependingupon operating conditions and other variables. In the frequency domain,arcing may be represented by an increase in energy in the broadbandspectrum. The energy released during arcing may be detectable atrelatively high frequencies within a frequency spectra (FIG. 7) of theoutput signal. It should be noted that an increase in energy may occurin the low-frequency portion (FIG. 7) of the frequency spectrum duringapplication of current to the electrical system 150 which may be theresult of arcing. However, the increase in energy in the low-frequencyportion may also be the result of electrical noise within the electricalsystem 150. Therefore, the test device 10 disclosed herein may beconfigured to perform separate evaluations of the low-frequency portionand the high-frequency portion (FIG. 7) in order to reliably detect theoccurrence of arcing within the electrical system 150.

Referring to FIG. 1, for the embodiment of the test device 10 configuredto detect arcing, the spectral analyzer 134 may be connected to theprobe element 50. The spectral analyzer 134 may also be connected to theprocessor 92 by one or more lines. The probe element 50 may also beconnected to the power supply 88 which may be connected to an externalpower source 90 such as a battery of a motor vehicle. The probe element50 may be placed in contact with the electrical system 150 and may beenergized by the power supply 88 in order to apply to the electricalsystem 150 an input signal containing current for measuring at least oneparameter of the electrical system 150 in a manner as described above.Upon application of current to the electrical system 150, the spectralanalyzer 134 may monitor the electrical system 150 for arcing behaviorin the presence of non-arcing signals. Advantageously, the spectralanalyzer 134 may monitor the electrical system 150 for arcing whilesimultaneously measuring the parameters of the electrical system 150.

The test device 10 may include a suitable sensing element (not shown)which may be a passive or active device such as a resistor (not shown)or an inductor (not shown). The sensing element may sample or monitoroutput signals for possible arcing in response to the application ofcurrent to the electrical system 150 when the input signal is applied tothe electrical system 150. The test device 10 may also include one ormore configurations of signal processing such as a digital signalprocessor 92 for examining the periodicity and/or spectrum of themonitored output signal in order to determine whether the output signalcontains arcing. As was earlier indicated, the occurrence of arcing maygenerate an increase in the broadband spectrum of the output signal,both in a low-frequency portion (FIG. 7) of the frequency spectra 140and in a high-frequency portion (FIG. 7) of the frequency spectra 140.However, an increase in energy in a low-frequency portion of thefrequency spectra 140 may be indicative of processes other than arcingsuch as electrical noise, and therefore may require an evaluation of thehigh-frequency portion of the spectrum in order to reliably determinethe occurrence of arcing. In this regard, the spectral analyzer 134 maybe configured to analyze a continuous spectra of low frequency and highfrequency energy of the output signal. The spectral analyzer 134 mayanalyze the power spectra density of the output signal as may bemeasured in power (i.e., watts/Hz) (FIG. 7) or in terms of voltage(i.e., volts/Hz) (FIG. 7).

Referring briefly to FIG. 7, the frequency spectra 140 of the outputsignal may include the low-frequency portion and the high-frequencyportion and may contain energy contributions from periodic signals 142(e.g., discrete signals) and energy contributions from non-periodicsignals 144. The low-frequency portion of the frequency spectra 140 maycontain a substantial majority of the periodic signals 142 in thefrequency spectra 140 relative to the quantity of the periodic signals142 that may be contained in the high-frequency portion. Conversely, thehigh-frequency portion of the frequency spectra 140 may contain asubstantial majority of the non-periodic signals 144 relative to thequantity of non-periodic signals 144 contained in the low-frequencyportion. In this regard, the low-frequency portion may be defined as thelocation where most of the known, periodic signals 142 reside and thelocation where the test device 10 is making measurements of voltage,current, and other parameters of the electrical system 150 under test.The high-frequency portion of the frequency spectra 140 may comprise theband of frequencies where a substantial portion of arcing power may becontained with relatively few periodic signals 142. For example, FIG. 9illustrates two periodic signals 142 in the low-frequency portion of thefrequency spectra 140 with no discernable periodic signals 142 occurringin the high-frequency portions.

The spectral analyzer 134 block of FIG. 1 may be configured to analyzethe spectral density of the low-frequency portion and detect, discern,or distinguish periodic signals 142 from non-periodic signals 144. Inthis regard, the spectral analyzer 134 block may be configured to detectthe potential occurrence of arcing in the electrical system 150 undertest when the energy contributed by the non-periodic signals 144 in thelow-frequency portion exceeds an energy threshold that may bepredetermined and/or preprogrammed into the test device 10. As indicatedabove, such periodic signals 142 may represent one or more of theparameters (i.e., voltage, current, etc.) being measured by the testdevice 10 during application of current to the electrical system 150. Ifthe energy in the low-frequency portion exceeds the predetermined energythreshold, the spectral analyzer 134 may then analyze the spectraldensity of the high-frequency portion. The spectral analyzer 134 mayreliably detect the occurrence of arcing when the energy in thehigh-frequency portion exceeds the predetermined energy threshold.

In an embodiment, the predetermined energy threshold may be the same forthe low-frequency portion and the high-frequency portion. However, theenergy threshold for the low-frequency portion may be different than theenergy threshold of the high-frequency portion. The spectral analyzer134 may be configured to analyze the high-frequency portion for arcingusing the high frequency energy threshold after the spectral analyzer134 detects the potential occurrence of arcing during analysis of thelow-frequency portion using the low frequency energy threshold. In thismanner, the test device 10 may be operated with a reduced sensitivityduring the initial analysis of the low-frequency portion of thefrequency spectra 140. Such reduced sensitivity of the test device 10may reduce the occurrence of a false positive or false alarm indetecting the potential occurrence of arcing when analyzing thelow-frequency portion.

The selection of the energy threshold may be based on historical dataregarding the magnitudes of arcing energy emitted by one or moreelectrical circuit systems such as automotive circuits tested under oneor more operating or testing conditions. Furthermore, the energythreshold may be based upon the minimum sensitivity of the test device10. As indicated above, if the energy threshold is set too low, veryweak levels of arcing may be detected which may create a large number offalse positives which may interrupt the overall test sequence that thetechnician is performing when testing multiple locations of anelectrical system 150 or when testing multiple electrical systems 150.Ideally, the predetermined energy threshold is selected to provide asubstantially reliable indication of arcing in a substantial majority ofelectrical circuits that may be tested using the test device 10. Forexample, the energy threshold, which may be different for thelow-frequency portion relative to the energy threshold of thehigh-frequency portion, may be selected to provide a probability ofgreater than approximately 80 percent that arcing is present in when theincrease in broadband energy of the frequency spectra 140 exceeds theenergy threshold. In this regard, the test device 10 may provide theability to adjust the energy threshold for different electrical system150 such that the energy threshold is compatible with the electricalsystems 150 to be tested.

In an embodiment, the spectral analyzer 134 (FIG. 1) may detect thepresence of arcing by first determining the total spectral power or thesum of arcing and non-arcing signals (i.e., respectably, non-periodicand periodic signals 142) contained within the frequency spectra 140 ofthe output signal. The output signal may be in the form of a voltagesignal, a power signal, or other suitable signal for analysis by thespectral analyzer 134. In this regard, the total spectral power may bemeasured in terms of power (e.g., watts/Hz) or in terms of voltage(e.g., volts/Hz) or in other terms. The spectral analyzer 134 may thendetermine the contribution of the periodic signals 142 to the totalspectral power. The periodic signals 142 may be identified and measuredby the existing functional blocks of the test device 10 as describedabove. For example, periodic signal 142 power may be a measuredparameter (i.e., voltage, frequency) of the electrical system 150 inresponse to application of the current to the electrical system 150. Thespectral analyzer 134 may then determine the contribution of thenon-periodic signals 144 as the difference between the total spectralpower and the contribution of the periodic signals 142.

The spectral analyzer 134 may determine the increase in the broadbandenergy of the frequency spectra 140 by comparing the contribution of thenon-periodic signals 144 to the total spectral power. The spectralanalyzer 134 may then determine whether the increase in the broadbandenergy exceeds a detection sensitivity of the test device 10. If thesensitivity of the test device 10 is not exceeded, the spectral analyzer134 may compare the increase in the broadband energy to thepredetermined energy threshold and may transmit a signal to anindicating device such as to the display device 54 or to the speakers 66to indicate when the increase in broadband energy exceeds the energythreshold. The processor 92 may be coupled to the spectral analyzer 134and may be configured to halt the application of current to theelectrical system 150 when the energy of a high-frequency portionexceeds the predetermined energy threshold as a means to avoid damage tothe electrical system 150 or to other components that may be arcing withthe electrical system 150.

As indicated earlier, the spectral analyzer 134 block (FIG. 1) may beequipped with spectral analysis circuitry such as digital signalprocessing software that can analyze the output signal in the frequencydomain and/or the time domain and measure the broadband low frequencyand high-frequency portions of energy present within the output signaland which may indicate the presence of arcing. The spectral analyzer 134block may employ a Fourier Transform or other suitable technique toobtain a spectral portrait of the output signal and facilitatediscernment of the contents of the low-frequency portion and thehigh-frequency portion of the frequency spectra 140 as shown in FIG. 7.The results of the arcing test may be displayed on the display device 54and/or may be indicated by the speaker 66 to alert the technician of theoccurrence of arcing. In this regard, the spectral analyzer 134 blockmay be configured to digitally process the output signal and analyze inthe frequency domain and/or the time domain the output signal fordetection of arcing during application of current to the electricalsystem 150. The testing of an electrical system 150 for arcing may occurcontinuously during measurement of the various parameters as current isapplied to the electrical system 150. Alternatively, the electricalsystem 150 may also be tested for arcing on an intermittent basis or ona preprogrammed basis.

Referring to FIG. 6, shown is a flow chart including one or moreoperations that may be performed during a method of detecting arcing inan electrical system 150. In step 602, the conductive probe element 50(FIG. 1) may be placed in contact with the electrical system 150 undertest as shown in FIG. 1. Power may be provided to the probe element 50from a power source such as an external power source 90 such as thebattery of a motor vehicle.

Step 606 of the method of FIG. 6 may comprise applying an input signalto the electrical system 150 (FIG. 1) using the conductive probe element50 (FIG. 1). The input signal may contain current to facilitate themeasurement of one or more parameters of the electrical system 150 aswas discussed above. The parameters may include circuit continuity,resistance, voltage, current, impedance, and other parameters.

Step 608 may comprise receiving an output signal from the electricalsystem 150 (FIG. 1) at the spectral analyzer 134 (FIG. 1). The outputsignal may be received in response to application of the input signal tothe electrical system 150. The output signal may be in the form of avoltage signal, a power signal, or other signal form. Step 608 mayfurther comprise analyzing, using the spectral analyzer 134, thefrequency spectra 140 (FIG. 7) of the output signal which may include alow-frequency portion (FIG. 7) and a high-frequency portion (FIG. 7). Asillustrated in FIG. 7, the frequency spectra 140 may contain energycontributed by periodic signals 142 and non-periodic signals 144 asdiscussed above.

Step 610 may comprise analyzing, using the spectral analyzer 134 (FIG.1), the low-frequency portion (FIG. 7), and detecting one or moreperiodic signals 142 (FIG. 7) among the non-periodic signals 144 (FIG.7) in the frequency spectra 140 (FIG. 7). The spectral analyzer 134 maybe configured to detect the potential occurrence of arcing in theelectrical system 150 when the energy contributed by the non-periodicsignals 144 in the low-frequency portion exceeds a predetermined energythreshold as illustrated in FIG. 7. The predetermined energy thresholdmay be programmed into the test device 10 as was indicated above toaccount for the sensitivity of the test device 10 and prevent falsepositives or false alarms during the sequential testing of a number orparameters of the electrical system 150 under test. In this regard, ifthe energy in the low-frequency portion exceeds the energy threshold instep 610, then the spectral analyzer 134 block analyzes thehigh-frequency portion.

In step 612, the spectral analyzer 134 (FIG. 1) may compare the energyin the high-frequency portion (FIG. 7) to a predetermined energythreshold which may be different than the energy threshold of thelow-frequency portion (FIG. 7). In step 614, the energy threshold in thehigh-frequency portion may be set or programmed into the test device 10in a manner to provide reliable detection of arcing as discussed above.

In step 616, the application of current to the electrical system 150 maybe halted when the energy of the high-frequency portion exceeds thepredetermined energy threshold which may be indicative of arcing in theelectrical system 150 under test. In this manner, the test device 10prevents damage that may otherwise occur to the electrical system 150 ifcurrent were continuously applied to the electrical system 150 undertest.

In step 618, if the energy in the high-frequency portion is less thanthe predetermined energy threshold, application of current to theelectrical system 150 may allow for continuing measurement of one ormore parameters of the electrical system 150. Such parameters that maybe measured by the test device 10 may include, but are not limited to,circuit continuity, resistance, voltage, current, impedance, andfrequency. In addition, the test device 10 may be configured to providea signal to an indicating device such as a display device 54 or aspeaker 66 to indicate to a user the occurrence of arcing in theelectrical system 150. As discussed above, the test device 10 may beconfigured such that the magnitude of the energy threshold may be set toprevent false alarms of the detection of arcing.

Referring to FIGS. 1 and 8, in a further embodiment, the test device 10may be configured to measure the health or integrity of relativelylow-impedance cables or electrical paths 156 (FIGS. 9A-9B). Themeasurement of low-impedance electrical paths 156 such as power feeds164 or power grounds 162 may be performed with the cooperation of thevoltage measurement A/D converter 126, the current measurement A/Dconverter 130, and optionally, the auxiliary ground lead 110. Thevoltage measurement A/D converter 126 and the current measurement A/Dconverter 130 may be operated in cooperation with the processor 92. Themeasurement of low-impedance electrical paths 156 may be facilitated byfirst applying a relatively low-amperage input signal to the electricalpath 156 and determining a first voltage. A relatively high-amperagecurrent pulse may then be applied to the electrical path 156 todetermine a second voltage. A voltage drop may be determined based onthe difference between the first voltage and the second voltage. Thetest device 10 may then calculate the electrical resistance of theelectrical path 156 based on the voltage drop and display the value ofthe voltage drop and/or provide a pass/fail indication regarding thehealth of the electrical path.

In the embodiment of the test device 10 (FIG. 1) for measuring thehealth of low-impedance electrical paths 156 (FIGS. 9A-9B), the testdevice 10 may include the power supply 88 (FIG. 1) and the probe element50 (FIG. 1). The power supply 88 may be connected to the external powersource 90 (FIG. 1). The probe element 50 may be placed in contact withthe electrical path 156 and energized by power from the power supply 88such that a relatively low-amperage input signal is applied to theelectrical path 156. The processor 92 (FIG. 1) or other functionalblocks discussed above may be connected to the probe element 50 and maybe configured to receive an output signal from the electrical path 156in order to determine the first voltage measurement across theelectrical path 156 in response to application of the low-amperage inputsignal.

The processor 92 may then be configured to apply the relativelyhigh-amperage current pulse to the electrical path 156 for a relativelyshort time period in order to determine a second voltage measurementacross electrical path 156 in response to application of thehigh-amperage current pulse. The processor 92 may then determine thedifference between the first voltage and the second voltage in order todetermine a voltage drop across the electrical path 156. The test device10 may include an indicating device such as a display device 54 orspeaker 66 that may be coupled to the processor 92 to provide anindication of the voltage drop and the electrical resistance of theelectrical path 156. As indicated above, the test device 10 may also beconfigured to provide a pass/fail indication of whether the voltage dropexceeds a maximum specified voltage drop for the electrical path 156. Inaddition, the test device 10 may provide an indication regarding whetherthe measurement of the current in the electrical path 156 is less thanmagnitude of the high-amperage current pulse applied to the electricalpath 156. The indication may in the form of an audible indication, avisual indication, or a tactile (i.e., vibration) indication, or anycombination thereof. During measurement of the second voltage, if themeasured current in the electrical path 156 is less than thehigh-amperage current pulse, the auxiliary ground lead 110 may beconnected from the test device 10 to the electrical path 156 to provideadditional current to the electrical path 156.

The processor 92 (FIG. 1) and the test device 10 (FIG. 1) may beconfigured to halt or prevent the application of the high-amperagecurrent pulse to the electrical path 156 when the first voltage fallsoutside of a predetermined or preset (e.g., normal) operating range ofthe electrical path 156. In this regard, during application of thelow-amperage input signal, the test device 10 may be configured tomonitor the electrical path 156 to determine whether the electrical path156 has any obvious faults and is durable enough to receive thehigh-amperage current pulse. For example, the electrical path 156 maycomprise a cable such as the power cable extending from a battery (notshown) of a motor vehicle (not shown) to a starter (not shown) of anengine (not shown) of the motor vehicle. If the application of therelatively low-amperage input signal to the electrical path 156 resultsin the first voltage being outside of the normal operating range for thepower cable, then the cable may have an obvious fault and may not bedurable enough to receive the high-amperage current pulse. In thisexample, the test of the electrical path 156 may be aborted in order tosafeguard the electrical system 150 from damage and avoid the risk ofdamage to any electrical circuits that may be connected to theelectrical path 156.

The magnitude of the high-amperage current pulse applied to theelectrical path 156 may be preprogrammed into the test device 10 and/ormay be manually adjustable. The magnitude of the high-amperage currentpulse may be dependent upon the capacity of the electrical path 156. Inan embodiment, the high-amperage current pulse may have an amperage ofat least approximately 10 amps. However, depending upon the operationand construction of the electrical path 156 or cable, the high-amperagecurrent pulse may have an amperage of up to 100 amps or more. Theduration or length of time during which the high-amperage current pulseis applied to the electrical path 156 may be relatively short to avoiddamage to the electrical path 156 or to components that may be connectedto the electrical path 156. In a non-limiting example, the high-amperagecurrent pulse may be applied to the electrical path 156 for a durationof less than approximately 5 milliseconds. However, longer or shorterdurations for application of the high-amperage current pulse arepossible. Advantageously, the test device 10 allows for testing thehealth and integrity of relatively low-impedance electrical paths orcables by contacting the probe element 50 to a single location on theelectrical path 156 instead of applying test devices 10 on opposite endsof the electrical path 156.

Referring to FIGS. 9A-9B, the test device 10 may be configured to testan electrical path 156 functioning as a power ground 162 (FIG. 9A) or asa power feed (FIG. 9B). In testing the integrity of a power ground 162(FIG. 9B), the probe element 50 may be placed in contact with ahigh-voltage side 158 of the power ground 162 and may source currentinto the power ground 162 in response to application of the relativelyhigh-amperage current pulse. The test device 10 (FIG. 1) may also beadapted to test an electrical path 156 functioning as a power feed 164(FIG. 9B) wherein the probe element 50 may be placed in contact with alow-voltage side 160 of the power feed 164. The probe element 50 may beconfigured to sink current from the power feed 164 into the test device10 using a load resistance (not shown) that may be integrated into thetest device 10. The probe element 50 may sink current from the powerfeed 164 into the test device 10 during application of the relativelyhigh-amperage current pulse. In each case of FIGS. 9A and 9B, theprocessor 92 may determine a second voltage across the electrical path156 in response to application of the relatively high-amperage currentpulse.

In the case of the power ground 162 (FIG. 9B) or power feed 164 (FIG.9B), the processor 92 may determine a voltage drop across the electricalpath 156 based on the difference between the first voltage (i.e.,measured during application of the low-amperage input signal) and thesecond voltage (i.e., measured during application of the high-amperagecurrent pulse). The test device 10 may be configured to determine anelectrical resistance of the electrical path 156 proportional to thevoltage drop across the power feed 164 or power ground 162. The testdevice 10 may be configured to provide an indication of whether theelectrical resistance of the power feed 164 or power ground 162 fallswithin the normal operating range. If a failure is detected in the powerfeed 164 or power ground 162 electrical paths 156 (i.e., electricresistances are below the normal operating range), the test device 10may be configured to display or otherwise indicate such failure. In thisregard, the voltage measurement A/D converter 126 and the currentmeasurement A/D converter 130 may respectively collect voltage andcurrent readings from the electrical path 156 and send such readings tothe processor 92. The processor 92 may take such readings or data andcompute the electrical resistance for the electrical path 156 under testand send a pass/fail result to the display device 54. As indicatedabove, a failure may be detected and displayed if a voltage drop exceedsa maximum voltage drop expected for the electrical path 156. A failuremay also be detected and displayed if the current flow within theelectrical path 156 is below the level that the test device 10 may applyto the electrical path 156 with the relatively high-amperage currentpulse.

Referring to FIG. 8, shown is a method for measuring a voltage dropand/or electrical resistance in a relatively low-impedance electricalpath 156 (FIG. 9A-9B). Step 802 of the method of FIG. 8 may includeplacing the conductive probe element 50 in contact with the electricalpath 156. Step 804 may comprise energizing the probe element 50 such asby using power from a power supply 88. Step 806 of the method of FIG. 8may include applying, using the probe element 50, a relativelylow-amperage input signal to the electrical path 156. Step 808 of themethod of FIG. 8 may comprise determining, using the processor 92, afirst voltage across the electrical path 156 in response to theapplication of a low-amperage input signal. Step 808 may includedetermining whether the first voltage within the electrical path 156resulting from application of the low-amperage input signal is within anormal operating range of the electrical path 156. Once the firstvoltage has been determined to be within the normal operating range ofthe electrical path 156, step 810 may comprise, using the probe element50, a relatively high-amperage current pulse to the electrical path 156.In this regard, a technician may depress a button on the keypad whichmay then display a ready indication on the display device 54. Thetechnician may then push the appropriate button on the keypad toinitiate application of the momentary high-amperage current pulse to theprobe element 50 and into the electrical path 156 under test. Thecurrent in the high-amperage current pulse may be supplied by the poweroutput driver with over current protection 128.

Step 812 may comprise determining, using the processor 92 and one ormore of the functioning blocks illustrated in FIG. 1, the second voltageacross the electrical path 156 in response to application of thehigh-amperage current pulse. Voltage and current readings may becollected by respective ones of the voltage measurement A/D converter126 and current measurement A/D converter 130 and sent to the processor92.

Step 814 may comprise determining, using the processor 92, a voltagedrop across the electrical path 156 based upon the difference betweenthe first voltage and the second voltage. The method of FIG. 8 mayinclude, indicating using an indicating device, the voltage drop, and/orelectrical resistance across the electrical path 156 based upon (i.e.,proportional to) the voltage drop. Step 816 of FIG. 8 may compriseproviding a pass/fail indication of whether the voltage drop exceeds themaximum specified voltage drop for the electrical path 156. A pass/failindication may also be provided if the measurement of current in theelectrical path 156 is less than the magnitude of the high-amperagecurrent pulse.

Step 818 of the method of FIG. 8 may include preventing the applicationof high-amperage current pulse to the electrical path 156 when the firstvoltage is outside of the normal operating range for the electrical path156. In this regard, step 818 may comprise aborting the test for theintegrity of low-impedance electrical path 156 in order to avoid therisk of damage to the electrical path 156 or any circuits that may beconnected to the electrical path 156 that may otherwise be caused byapplication of the high-amperage current pulse.

Referring again briefly to FIGS. 9A and 9B, the method of testing theintegrity or health of an electrical path 156 may also comprise testinga power feed 164 or a power ground 162. As shown in FIGS. 9A and 9B, theelectrical path 156 may have a high-voltage side 158 and a low-voltageside 160. For testing a power ground 162, the probe element 50 may beplaced in contact with the high-voltage side 158. In FIG. 9A, the methodmay include applying the relatively low-amperage input signal to theelectrical path 156 at the high-voltage side 158 of the power ground162. If the first voltage measured by the test device 10 falls withinthe normal operating range for the electrical path 156, then therelatively high-amperage current pulse may be sunk into the test device10 by means of a load resistance that may be incorporated into the testdevice 10. The processor 92 may determine a second voltage of theelectrical path 156 in response to application of the high-amperagecurrent pulse and may calculate the voltage drop and/or the electricalresistance of the power ground 162 electrical path 156 based upon thedifference between the first voltage and the second voltage.

In FIG. 9B, for electrical paths 156 functioning as power feeds 164, theprobe element 50 may be placed into contact with the low-voltage side160 of the electrical path 156. The relatively low-amperage input signalmay be applied to the electrical path 156 at the low-voltage side 160 ofthe power feed 164 and a first voltage may be determined. If the firstvoltage measured by the test device 10 falls within the normal operatingrange for the electrical path 156, then the high-amperage current pulsemay be sourced into the electrical path 156 from the test device 10. Thesecond voltage may be then determined and compared to the first voltageto arrive at the voltage drop across the power ground 162 electricalpath 156. Electrical resistance may also be determined and compared tothe specified resistance for the electrical path 156 to determine theintegrity of the electrical path 156.

Advantageously, in testing relatively low-impedance electrical paths 156of cables using the test device 10 and method described above in theexamples shown in FIGS. 9A and 9B, a user may safely evaluate theintegrity of the electrical path 156 or cable without disconnecting orremoving the electrical path 156 from the electrical system 150. Thehigh-amperage current pulse is advantageously applied over a relativelyshort time period to avoid damage to the electrical path 156. However,the high-amperage current pulse is applied for a long enough duration toacquire the second voltage measurement that may be used to determine thevoltage drop across the electrical path 156 and provide an accurateassessment of the electrical resistance of the electrical path 156.

In any one of the above-described embodiments of this device,measurement of any one of the parameters such as voltage, resistance,frequency, DC voltage, DC current, and AC voltage, may be performed in asequential manner without user intervention and without manual selectionof the parameter to be measured. In this manner, sequential measurementof one or more parameters may free up one or both hand of a user toallow the efficient testing of various portions of a diagnosticsequence. In this regard, the test device 10 as disclosed here mayfacilitate automatic scanning of a multiplicity of parameters of anelectrical system 150 under test and automatically select the parameterto be tested and displayed. In an embodiment, the test device 10 may beconfigured such that more than one parameter may be displayed in asequence after measuring a plurality of parameters.

Referring now to FIGS. 1 and 10, any of the embodiments of the testdevice 10 disclosed herein may include the capability to sequentiallymeasure a variety of parameters of an electrical system 150 under testwithout user invention. The test device 10 may facilitate automaticsequential measurement of the parameters with the cooperation of theload impedance detector 120 block, the frequency and totalizermeasurement 124 block, the voltage measurement A/D converter 126 block,the resistance measurement 132 block, and the processor 92. The keypadof the test device 10 may include one or more buttons or switches whichmay be activated to initiate the automatic sequencing of the measuringof various parameters.

The flow chart in FIG. 10 illustrates one or more operations that may beperformed during sequential measurement of one or more parameters of anelectrical system 150 under test. In step 1002, the probe element 50 maybe placed in contact with the electrical system 150 under test. Afterplacing the probe element 50 in contact with the electrical system 150,in step 1004, current may be applied to the electrical system 150 byactivating a switch or button on the keypad. In step 1006, the testdevice 10 may measure the current (e.g., in terms of amperage) and/orresistance (e.g., in terms of ohms) in the electrical system 150 inresponse to application of the input signal. The display device 54 maydisplay a reading of the amperage and/or a reading of the ohms measuredduring application of the input signal to the electrical system 150.

In step 1008, the test device 10 may initiate automatic measurement ofone or more parameters of the electrical system 150 without accessingthe keypad to select a parameter to be measured. During such automaticsequential measurement, the functional blocks for low-impedancedetection 120, frequency measurement 124, voltage measurement 126, andresistance measurement 132 (FIG. 1) may be coordinated by the processor92 to sequence the test device 10 in a logical manner to prevent damageto the electrical system 150 and to the test device 10. The displaydevice 54 and/or the speaker 66 may be used to provide an indication ofthe measurement of such parameters such as an audible signal or a visualindication of measured parameters.

The test device 10 may be configured to begin measurement of the mostdominating parameter or the parameter which prevents other parametersfrom being measured. For example, voltage of the electrical system 150may be the initial parameter measured. If a voltage reading is detectedand measured, the voltage measurement may be displayed and/or stored inthe test device 10 in step 1010. The next most sensitive measurement maythen be measured such as, for example, a measurement of resistance instep 1012 (FIG. 10) using the resistance measurement 132 blockillustrated in FIG. 1. The resistance measurement may be displayed by adisplay device 54 in step 1014. The test device 10 may be configured toinsert or apply an input signal of current to the electrical system 150via the probe element 50 to provide the capability for measuring theelectrical resistance.

Step 1016 may comprise measuring a frequency of the electrical system150 in response to application of the input signal containing current.Upon measurement of the frequency, step 1018 may comprise displaying thefrequency on the display device 54 or providing an audible indication ofthe measurement of the frequency such as through the speakers 66. Step1020 may comprise detecting the presence of an AC voltage in anelectrical system 150. Detection and measurement of the AC voltage in anelectrical system 150, step 1022 may comprise displaying the measurementof the AC voltage such as on the display device 54. As may beappreciated, the sequential measurement of the parameters may include avariety of other parameters not described above and/or not illustratedin FIG. 10.

By proceeding in a manner described above and illustrated in FIG. 10,the processor 92 and/or test device 10 may coordinate the measurement ofone or more parameters of the electrical system 150 in an automaticand/or pre-defined sequence. The display device 54 and/or speaker 66 maybe used to notify the user of stored data. An alert may be sounded bythe speaker 66 when all parameters have been measured and to notify theuser of the conclusion of all possible measurements at the particularnode in the electrical system 150. In this manner, the technician mayefficiently move the probe element 50 to a different position on theelectrical system 150 or to another electrical system 150 for initiatinganother sequence of automatic measurements. In an embodiment, thespeaker 66 may be configured to provide audible feedback to the userregarding which parameter is being measured and avoiding the need forthe user to constantly view the display to determine which parameter isbeing measured. Optionally, at any point during the testing sequence,the test device 10 may be moved into a manual mode wherein the user maymanually select which parameters are to be measured. For example, a usermay halt the automatic sequencing of the measurement of parameters bymanipulating the keypad and entering a manually controlled and morefocused sequence for measuring one or more particular parameters ofinterest.

Additional modifications and improvements of the present disclosure maybe apparent to those of ordinary skill in the art. Thus, the particularcombination of parts described and illustrated herein is intended torepresent only certain embodiments of the present disclosure and is notintended to serve as limitations of alternative embodiments or deviceswithin the spirit and scope of the disclosure.

What is claimed is:
 1. An electrical test device adapted to applycurrent to an electrical system during measurement of a plurality ofparameters, comprising: a power supply connected to an external powersource; a conductive probe element configured to be energized by thepower supply, the probe element being configured to be placed in contactwith an electrical system and apply to the electrical system an inputsignal containing current for measuring at least one parameter of theelectrical system; a spectral analysis block connected to the probeelement and being configured to perform the following: receive an outputsignal from the electrical system in response to application of theinput signal; analyze a frequency spectra of the output signal, thefrequency spectra having a low-frequency portion and a high-frequencyportion and containing energy contributed by the periodic andnon-periodic signals, analyze the low-frequency portion and detect thepotential occurrence of arcing in the electrical system when the energycontributed by the non-periodic signals in the low-frequency portionexceeds a predetermined energy threshold, analyze the high-frequencyportion when the energy in the low-frequency portion exceeds the energythreshold and detect the occurrence of arcing in the electrical systemwhen the energy in the high-frequency portion exceeds the energythreshold.
 2. The electrical test device of claim 1 further comprising:an indicating device coupled to the spectral analysis block and beingconfigured to indicate the occurrence of the arcing in the electricalsystem when the energy in the high-frequency portion exceeds the energythreshold.
 3. The electrical test device of claim 1 wherein: the testdevice is programmable with a low-frequency energy threshold and ahigh-frequency energy threshold; the spectral analysis block beingconfigured to analyze the high-frequency portion for arcing in theelectrical system using the high-frequency energy threshold after thespectral analysis block detects the potential occurrence of arcingduring analysis of the low-frequency portion using the low-frequencyenergy threshold.
 4. The electrical test device of claim 1 furthercomprising: a processor coupled to the spectral analysis block and beingconfigured to halt the application of current to the electrical systemwhen the energy of the high-frequency portion exceeds the predeterminedenergy threshold.
 5. The electrical test device of claim 1 wherein: theoutput signal is in the form of at least one of the following: a voltagesignal, a power signal.
 6. The electrical test device of claim 1wherein: the test device is configured to sequentially measure at leasttwo of the following parameters without user intervention during theapplication of current to the electrical system: DC voltage, DC current,AC voltage, frequency, resistance.
 7. A method of detecting arcing in anelectrical system, comprising the steps of: placing a conductive probeelement in contact with an electrical system; providing power to theconductive probe element from an external power source; applying aninput signal to the electrical system, the input signal containingcurrent; receiving an output signal from the electrical system inresponse to the application of the input signal to the electricalsystem; analyzing a frequency spectra of the output signal, thefrequency spectra having a low-frequency portion and a high-frequencyportion and containing energy contributed by the periodic andnon-periodic signals; analyzing the low-frequency portion and detectingthe potential occurrence of arcing in the electrical system when theenergy contributed by the non-periodic signals in the low-frequencyportion exceeds a predetermined energy threshold; and analyzing thehigh-frequency portion when the energy in the low-frequency portionexceeds the energy threshold and detect the occurrence of arcing in theelectrical system when the energy in the high-frequency portion exceedsthe energy threshold.
 8. The method of claim 7 further comprising thestep of: halting the application of current to the electrical systemwhen the energy of the high-frequency portion exceeds the predeterminedenergy threshold.
 9. The method of claim 7 further comprising the stepof: measuring at least one of the following parameters during thedetection of arcing in the electrical system: circuit continuity,resistance, voltage, current, load impedance, and frequency.
 10. Themethod of claim 9 further comprising the steps of: continuously samplingthe output signal during the application of current to the electricalsystem; and sequentially measuring at least two of the parameterswithout user intervention during the application of current to theelectrical system.
 11. An electrical test device, comprising: a powersupply connected to an external power source; a conductive probe elementconfigured to be placed in contact with an electrical path of anelectrical system and energized by the power supply for applying to theelectrical path an input signal of relatively low-amperage; and aprocessor connected to the probe element and being configured to receivean output signal from the electrical path and determine a first voltageacross the electrical path in response to the low-amperage input signal;the processor being configured to apply a relatively high-amperagecurrent pulse to the electrical path and determine a second voltageacross the electrical path in response to application of thehigh-amperage current pulse; the processor being configured to determinea voltage drop across the electrical path based on the differencebetween the first voltage and the second voltage.
 12. The electricaltest device of claim 11 wherein: the electrical path has a normaloperating range; and the processor being configured to prevent theapplication of the high-amperage current pulse to the electrical pathwhen the first voltage is outside of the normal operating range.
 13. Theelectrical test device of claim 11 wherein: the electrical pathcomprises a power feed having a high-voltage side and a low-voltageside; the probe element being configured to be placed in contact withthe low-voltage side; and the probe element being configured to sinkcurrent into the test device during application of the relativelyhigh-amperage current pulse.
 14. The electrical test device of claim 11wherein: the electrical path comprises a power ground having ahigh-voltage side and a low-voltage side; the probe element beingconfigured to be placed in contact with the high-voltage side; and theprobe element being configured to source current into the electricalpath during application of the relatively high-amperage current pulse.15. The electrical test device of claim 11 wherein: the processor beingconfigured to determine an electrical resistance of the electrical pathbased on the voltage drop.
 16. A method of measuring a voltage drop in arelatively low-impedance electrical path, comprising the steps of:placing a conductive probe element in contact with the electrical path;energizing the probe element from an power supply; applying, using theprobe element, a relatively low-amperage input signal to the electricalpath using the probe element; determining, using the processor, a firstvoltage across the electrical path in response to the application of thelow-amperage input signal; applying, using the probe element, arelatively high-amperage current pulse to the electrical path;determining, using the processor, a second voltage across the electricalpath in response to the application of the high-amperage current pulse;and determining, using the processor, a voltage drop across theelectrical path based on the difference between the first voltage andthe second voltage.
 17. The method of claim 16 further comprising thestep of: indicating, using an indicating device, the voltage drop acrossthe electrical path.
 18. The method of claim 17 wherein the electricalpath has a normal operating range, the method further comprising thestep of: preventing the application of the high-amperage current pulseto the electrical path when the first voltage is outside of the normaloperating range.
 19. The method of claim 17 wherein the electrical pathcomprises a power feed having a high-voltage side and a low-voltageside, the method further comprising the steps of: placing the probeelement in contact with the low-voltage side; and sinking current fromthe electrical path into the test device during application of thecurrent pulse.
 20. The method of claim 17 wherein the electrical pathcomprises a power ground having a high-voltage side and a low-voltageside, the method further comprising the steps of: placing the probeelement in contact with the high-voltage side; and sourcing current fromthe test device into the electrical path during application of thecurrent pulse.